"Vitamin D has been known for many years to play a critical role in skeletal health, such that very low levels of this hormone (less than 20 nanomoles per liter) can cause osteomalacia, a disorder of impaired bone mineralization," write Andrew Grey, M.D., and Mark Bolland, M.B.Ch.B., Ph.D., of University of Auckland, New Zealand, in an accompanying editorial. "More recently, observational studies have reported inverse associations between levels of serum 25-hydroxyvitamin D, the metabolite that best reflects overall vitamin D status, and the risk of a wide range of disease, including cancer, vascular disease, infectious conditions, autoimmune diseases, osteoporosis, type 2 diabetes mellitus and obesity.""The results of these observational studies have prompted calls for widespread treatment of individuals with low levels of vitamin D and the establishment of public health programs aimed at raising the population levels of vitamin D to 'healthy' values," the authors write."It is now time to test the various hypotheses generated by observational studies of vitamin D, including that of Llewellyn et al, in adequately designed and conducted randomized controlled trials," they conclude. "Very importantly, such trials will also provide an opportunity to systematically assess potential harms of vitamin D supplementation, an issue that has been largely overlooked or dismissed. We should invest in trials that provide the best possible evidence on the benefits and risks of vitamin D before we invest in costly, difficult and potentially unrewarding interventional strategies."

SOURCE Archives of Internal Medicine